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ICJ 8921 



Bureau of Mines Information Circular/1983 




Methods for Determining Sources 
of Mercury Vapor in the Workplace 

By D. L. Neylan, H. C. Triantafillou, and S. L. Law 




UNITED STATES DEPARTMENT OF THE INTERIOR 



Information Circular 8921 



Methods for Determining Sources 
of Mercury Vapor in the Workplace 

By D. L. Neylan, H. C. Triantafillou, and S. L. Law 




UNITED STATES DEPARTMENT OF THE INTERIOR 
James G. Watt, Secretary 

BUREAU OF MINES 
Robert C. Horton, Director 



Mi 



This publication has been cataloged as follows: 



Neylan, D. L, (David L.) 

Methods for determining sources c 

(Information circular / United Sta 
reau of Mines ; 8921) 

Bibliography: p. 15 . , 

Supt. of Docs, no.: I 28.27:8921. 

1. Air pollution— Measurement. 2. 
dustries — Environmental aspects. I. 
II. Law, Stephen L. III. Title. IV. S< 
States. Bureau of Mines) ; 8921. 


f mercury vapor in the workplace. 
:es Department of the Interior, Bu- 

Mercury — Analysis. 3. Mineral in- 

Triantafillou, H. C. (Heidi C). 

;ries: Information circular (United 

622s [622\8] 82-600371 


HNzytJ.U4 L 1 JJoo (Jvloi J 



Or 






ft. 



CONTENTS 

Page 



Abstract 1 

Introduction 1 

Chemical spot tests 2 

Sensitivity 7 

Reagent shelf life 7 

Spot test techniques 8 

Selected spot tests 9 

Mercury vapor test papers 10 

Portable mercury vapor detectors 11 

Portable analytical Instruments 13 

Conclusions 14 

References 15 

ILLUSTRATION 

1. Gold-film analyzer for locating sources of mercury vapor 12 

TABLES 

1 . Reagents for mercury detection 2 

2. Portable mercury vapor detection devices 11 

3. Portable analytical instruments 13 



*0 



UNIT 


OF MEASURE ABBREVIATIONS 


USED IN 


THIS REPORT 


cm 


centimeter 


mg/m 3 


milligram per 
cubic meter 


g 


gram 










mm 


millimeter 


m3 


cubic meter 










nm 


nanometer 


mg 


milligram 










Mg 


microgram 


mL 


milliliter 










M L 


microliter 



METHODS FOR DETERMINING SOURCES OF MERCURY VAPOR IN THE WORKPLACE 

By D. L. Neylan, 1 H. C. Triantafillou, 2 and S. L. Law 3 



ABSTRACT 

The Bureau of Mines evaluated various methods for identifying sources 
of mercury vapor in excess of the threshold limit value (TLV) of 0.05 mg 
of mercury per cubic meter of air set by the American Council of Govern- 
ment and Industrial Hygienists (ACGIH) for mines and mineral processing 
plants. Chemical spot tests and portable devices for mercury determina- 
tion were evaluated, based on information from published sources and 
performance in laboratory tests. Among the parameters examined were 
sensitivity, interferences, cost, ease of use, and other factors perti- 
nent to field application. More than 50 methods were evaluated. 

The investigators found that many readily available methods are suita- 
ble for identifying sources of mercury vapor in mines and mineral pro- 
cessing plants. The best method appears to be one that uses a commer- 
cially available mercury test paper sensitive only to mercuric ions. 

For some of the more promising chemical spot tests, this report in- 
cludes step-by-step instructions for field application. 

INTRODUCTION 

In order to enable the mining and mineral processing industry to com- 
ply with Federal regulations and to ensure workers' health, portable 
methods are needed for the on-site identification of sources of mercury 
vapor. In this report, many such methods are evaluated. 

Although the TLV for mercury vapor in mines and mineral processing 
plants is set by ACGIH, Part 30 of the Code of Federal Regulations as- 
signs enforcement of this limit to the Mine Safety and Health Adminis- 
tration (MSHA). At MSHA's request, the Bureau undertook the evaluation 
of chemical spot tests and instrumental methods for mercury determina- 
tion described in this report. A commercially available mercury test 
paper evaluated by the Bureau as the best indicator for mercury is cur- 
rently under study by MSHA for possible routine use in mine and mineral 
processing plant inspections. 

i Research chemist. 
^Chemist. 

3 Research supervisor. 
All authors are with the Bureau of Mines, Avondale Research Center, Avondale, Md. 



CHEMICAL SPOT TESTS 



Spot tests are portable, provide on- 
site results, and are less expensive than 
other qualitative methods for determining 
the presence of metal ions. Because spot 
tests offer these advantages, the Bureau 
evaluated more than 50 spot test reagents 
to determine their suitability for iden- 
tifying sources of mercury vapor in mines 
and mineral processing plants. These re- 
agents are listed in table 1. For each 
reagent, the table lists the positive re- 
sults observed when mercury is present, 
sensitivities, and interferences. 

Generally, chemical reagents will not 
react directly with mercury or undis- 
solved minerals containing mercury. 
Therefore, dissolution of some of the 
mercury-containing material with an ap- 
propriate acid is usually the first step 
in a chemical spot test. To achieve the 
desired test reaction, it may also be 
necessary to further adjust the dissolved 



mercury to the mercuric or mercurous va- 
lence state, adjust the acidity of the 
mercury and acid solution, or take other 
steps. The references in the last column 
of table 1 provide the guidance needed to 
perform spot tests using each of the 
listed reagents, and for some of the re- 
agents an additional source of informa- 
tion is cited. 

Table 1 does not list all the reported 
chemical methods for detecting mercury; 
only those for which sensitivities could 
be found are listed. Additional tests 
are mentioned by Feigl (2^,4 Welcher (11- 
14), and others. However, most, if not 
all, of the tests in popular use are sum- 
marized in table 1. 

^Underlined numbers in parentheses re- 
fer to items in the list of references at 
the end of this report. 



TABLE 1. - Reagents for mercury detection 



Reagent ' 



Reaction indica- 
tive of mercury 



Sensitivity, 
Ug Hg 



Comments 



Refer- 
ences 2 



ORGANIC REAGENTS 



Acridine thiocyanate 3 . 


Yellow needles .... 


0.5 


Yellow crystals also 
formed by Bi, Cd, 
U, Zn. 


13 




Dark precipitate. . 


100 


Reacts only with Hg + 
ion. 


11 




Colorless needles. 


.06 


Precipitates also 
formed by Ag, Ce, 
Co, Cu, Fe, Pd, Zn. 


12 




Reddish-violet 
color with Hg 2 2+ ; 
bluish-gray ring 
with Hg 2+ . 


40 
15 


Also reacts with Ag, 
Al, Mg, U. 


14 






20 


Forms a violet-red 
ring with Pb. 


14 




Crystals or 
precipitate. 


.5 


Also reacts with As, 
Bi, Cd, Ce, Cr, Cu, 
Pb, Sn, Zn, and 
others. 


14 







See footnotes at end of table. 



TABLE 1. - Reagents for mercury detection — Continued 



Reagent 



Reaction indica- 
tive of mercury 



Sensitivity, 
US Hg 



Comments 



Refer- 
ences 2 



ORGANIC REAGENTS— Continued 





Pink to red color. 


.1 


Also reacts with 
Ag , Au , Cu , Os , Pd . 
Ammonium chlorstan- 
nate causes the 
color. 


14 






2-Carboxyphenyl-5- 
azo-8-hydroxyquino- 
line. 


Rose-violet 
precipitate. 


200 


Also reacts with Ag, 
As, Co, Cr, Cu, Ni, 
Pd. 


11 




Bright yellow 
precipitate. 


10 


Ag, Fe, Ti inter- 
fere. No reaction 
with mercury 
chlorides. 


2, 11 


2 , 3-Diaminophenazine . . 


Red precipitate... 


10 


Also reacts with Cu. 
Fe and ammonia 
interfere. 


12 


Diethylaminophenyl- 
imi no camphor. 


Rich pink or scar- 
let color. 


20 


Color from Hg 2+ van- 
ishes upon exposure 
to ammonia; color 
from Hg 2 2+ turns 
black upon exposure 
to ammonia. Also 
reacts with Ag and 
Bi. 


13 


p-Dimethylaminobenzal- 
rhodanine. 


Pved-violet color 
or precipitate. 


.33 


In the presence of 
chlorides, acetate 
must be added. Al- 
so reacts with Ag 
and Cu. 


13 


Dimethylaminophenyl- 
iminocamphor . 


Rich pink or scar- 
let color. 


20 


Color from Hg 2+ 
vanishes and color 
from Hg 2 2+ turns 
black upon exposure 
to ammonia. Also 
reacts with Ag and 
Bi. 


13 


Di-a-naphthylcarba- 
zone. 


Gray-violet color. 


.05 


Also reacts with Cd, 
Cu, Fe, Mo. 


13 


Di-3-naphthylcarba- 
zone. 




.015 




13 


Di-( O-nit rophenyl ) 
carbazone. 


Gray-blue color... 


.08 


Also reacts with Cu, 
Fe, Mo. 


13 



See footnotes at end of table. 



TABLE 1. - Reagents for mercury detection — Continued 



Reagent 



Reaction indica- 
tive of mercury 



Sensitivity, 
yg Hg 



Comments 



Refer- 
ences 2 



ORGANIC REAGENTS— Continued 



Di-(m-nitrophenyl) 
carbazone. 


Red-brown color... 


.05 


Also reacts with Cu, 
Fe, Mo. 


13 


Di-(p-nitrophenyl) 
carbazone. 




.025 


do 


13 








Violet or blue 
precipitate. 


1 


Also reacts with Cd, 
Cr, Cu, Mo. Chlo- 
rides interfere. 


2, 13 






.05 


Also reacts with Cd, 
Co, Cr, Cu, Fe, Ni, 
Pb, Zn. 


2, 13 




Yellow or brown 
crystals. 


400 


Also reacts with Al, 
Be, Co, Cr, Cu, Fe, 
Ni, Zr. 


14 






.25 


Reacts with many 
metal ions. In 
acid solution, Au, 
Bi, Cu, Pt metals, 
Sb, Sn are main 
interf erents. 


2, 13 








Pink precipitate. . 


10,000 


Reacts only with 
Hg 2 2+ . 


14 






Hexamethylenetetra- 
mine. 5 


Light yellow color 


.035 


Color results from 
addition of iodide. 
Also reacts with 
Ca, Li, Mg, others. 


13 




Gray precipitate.. 


10,000 


Reaction is with 
Hg 2 2+ ions. Also 
reacts with Sb and 
Sn. 


14 


Methylene blue iodide. 




.021 


Also reacts with Ag 
and Sn. 


14 


ct-Naphthylamine 3 » 5 . . . . 


Yellow precipitate 


37 


Also reacts with Cr, 
Cu, Au, W, others. 


12 


o-Nitrosophenol 3 > 4 . . . . 


Reddish-violet 
solid. 


.1 


Reacts only with 
Hg 2+ ; similar re- 
sults with Cu 2+ , 
Ni, Zn, Fe 2+ . 


13 



See footnotes at end of table. 



TABLE 1. - Reagents for mercury detection — Continued 



Reagent 



Reaction indica- 
tive of mercury 



Sensitivity, 
Ug Hg 



Comments 



Refer- 
ences 2 



ORGANIC REAGENTS— Continued 



Phenyl-5-azo-8- 
hydroxy quinoline . 


Violet precipitate 


100 


Also reacts with Cu, 
Au, Mo, Ni, Pd, Zn. 


11 


Phenylhydrazinephenyl- 
thiocarbazinate. 3 


Reddish-purple 
precipitate. 


10 


Excess reagent must 
be avoided. Cr0 4 2- , 
Mo0 4 2-, V0 3 ~ 
interfere. 


14 


Phenylthiodantoic acid 


Yellow precipitate 


5 


Similar results are 
obtained with Cu, 
Bi, Sb. 


14 




Grayish-black 
precipitate. 


20 


Reaction is with 
Hg 2 2+ ion. Sensi- 
tivity of 20 yg is 
for Hg 2 2+ ; sensi- 
tivity for Hg 2+ is 
1,000 yg. Also re- 
acts with Ag, Cu + , 
Au-5 + , Pd 2 + , Pt4 + . 


14 




Red precipitate... 


20 


Reacts in the pres- 
ence of sodium 
acetate. 


13 










20 


Br", Cl~, I", CN~, 
SCN" interfere. 
Also reacts with 
Cr, Fe, Sb, Sn. 


11 




Yellow precipitate 


.15 


Also reacts with Ba, 
Cd, Cu, Fe, Ni, Ag, 
and many others. 


14 




Red precipitate... 


4,000 


Forms a violet pre- 
cipitate with Ag. 


13 








Colorless needles. 


.32 


Also reacts with Bi, 
Cd, Co, Sn, and 
others. 


13 








Dark red 
precipitate. 


1,000 


Also reacts with Au, 
Bi, Mo, Sb, W, and 
others. 


14 






Sodium diethyldithio- 
carbamate. 




100 


Reaction is with 
Hg 2+ . Also reacts 
with Cd, Co, Mn, 
Pb, Sr, Zn. 


14 



See footnotes at end of table. 



TABLE 1, - Reagents for mercury detection — Continued 



Reagent 1 



Reaction indica- 
t ive of mercury 



Sensitivity, 
Mg Hg 



Comments 



Refer- 
ences 2 



ORGANIC REAGENTS— Continued 





Yellow precipitate 


5 


Reaction is with 
Hg 2 2+ . Also reacts 
with Ag, Pb, Tl, 
N0 2 ~. 


11 






5-(p-Sulf ophenylazo)- 
8-hydroxyquinoline . 


Bright red 
precipitate. 


50 


Cl~ interferes. Re- 
acts also with Cu, 
Ni, Pd. 


11 




Yellow-white 
precipitate. 


10,000 


Reacts with many 
ionic species. 


12 






Tetramethyl-p-phenyl- 
enediamine (Wurster's 
reagent) , 3 


Violet precipitate 


1 


Also reacts with Ag, 
Cu, Fe, Os. 


12 




Rose-colored 
solution. 


1 


Also reacts with Cu, 
Zn. 


14 









INORGANIC 


REAGENTS 










0.0001 


Neutral solution 
needed. Hg is 
amalgamated with 
Al using current 
from a flashlight 
battery; alumina 


2 














formed gives red 
color with Alizarin. 






Deep red to orange 
color. 


.003 


Oxidants, Ag, Au, Mo, 
Pd, Pt, W interfere. 


2 


Hydrogen sulfide and 
formic acid. 3 


Colored colloidal 
suspension. , 


10 


Also reacts with As 
and Pb. Colorimeter 
used for detection. 


12 


Hypophosphite-tin-IV. . 


Red or light pink 
color. 


.1 


Cacotheline used to 
form color with 
tin-II. Ag, Os , 
and noble metals 
interfere. 


2 




Absence of blue 
color in test 
solution. 


.14 


Same reaction with 
Ag. 


14 






.02 


I 2 is dissolved in 
equal amounts of 
ethanol and toluene. 


11 









See footnotes at end of table. 



TABLE 1. - Reagents for mercury detection — Continued 



Reagent 



Reaction indica- 
tive of mercury 



Sensitivity, 
pg Hg 



Comments 



Refer- 
ences 2 





INORGANIC REAGENTS- 


-Continued 




Potassium dichromate- 
pyridine. 3 * 5 


Orange crystals . . . 




.075 


Both Hg 2 2+ and Hg2+ 
cause the reaction. 


13 


Potassium iodide- 
glycerol. 


Black precipitate. 




50 


Ag, Pb, Tl also 
precipitate with 
iodide, but are 
avoided in the 
test. 


11 


Stannous chloride- 
aniline. 3 


Brown, gray, 
or black 
precipitate. 




1 


Aniline is used to 
provide proper al- 
kalinity and avoid 
Sb interference. 
Ag may interfere. 


2 



1 A11 reagents should be considered hazardous. Before use, properties such as tox- 
icity, carcinogenicity, explosibility , etc. , should be determined by consulting such 
references as "Cancer Causing Chemicals" by N. I. Sax (Van Nostrand-Reinhold, New 
York, 1981, 466 pp.), "Dangerous Properties of Industrial Materials" by N. I. Sax 
(Van Nostrand-Reinhold, New York, 5th ed. , 1979, 1258 pp.), "Handbook of Reactive 
Chemical Hazards" by L. Bretherick (CRC Press, Inc., Boca Raton, Fla. , 1975, 976 
pp.), and "The Merck Index" (Merck and Co., Inc., Rahway, N.J. , 9th ed. , 1976, 1313 
pp.). For the reagents listed above, no listed hazards were found except as other- 
wise noted. 

2 For each reagent, these references generally give the chemical symbol, molecular 
weight, alternate nomenclature, and guidance for performing spot tests; for the less 
common organic compounds, preparation procedures are also given. 

3 Has toxic properties ranging from irritant to highly poisonous. 

4 Explosive or flammable. 

^Possible or known carcinogen. 



SENSITIVITY 

The sensitivities of the spot test 
reagents listed in table 1 range from 
0.0001 to 10,000 yg. If the mercury to 
be determined is in a form that dis- 
solves slowly in acid, the more sensi- 
tive reagents are recommended because 
they minimize the time needed to obtain 
a positive test. However, if a reagent 
is to be used to locate fine droplets 
of a mercury spill, and low levels of 
mercury or mercury compounds with low 
solubility are not of interest, it may 
be better to use one of the less sensi- 
tive reagents that will test positive 
only for relatively high levels of dis- 
solved mercury. For example, a reagent 
sensitive to mercury at the 10,000-yg 
level will detect — though perhaps with a 
weak color change — a droplet of mercury 



(density 13.6 g/cm 3 ) that is only 0.0007 
cm 3 in volume. 

For locating sources of mercury vapor 
in the workplace, test reagents of inter- 
mediate sensitivities are recommended. 
Their use avoids positive results for 
trace amounts of mercury but produces 
strong color changes for readily soluble 
forms of mercury at part-per-million lev- 
els of concentration. 

REAGENT SHELF LIFE 

Several of the reagents listed in 
table 1 need to be prepared fresh daily 
because they deteriorate rapidly upon 
exposure to actinic light (ultraviolet 
radiation capable of initiating photo- 
chemical reactions) or oxidation by 
air. These reagents would not generally 



be considered for field applications. 
In laboratory testing of various re- 
agents, it was found that chronotropic 
acid, Wurster's reagent (tetramethyl-p- 
phenylenediamine) , and dithizone contin- 
ued to give positive results for over 4 
weeks after preparation if stored in low- 
actinic-glass (colored glass that absorbs 
actinic light) containers and kept out of 
direct sunlight. When stored in clear 
glass containers, all three were ineffec- 
tive within 4 days of preparation. Dith- 
izone changed to an ineffective yellow 
solution after only 1 day of exposure to 
sunlight. By comparison, symdiphenyl 
carbazide showed no effect from exposure 
to the direct sunlight. As a rule of 
thumb, all reagents should be prepared 
fresh, kept away from heat, and stored 
or carried in light-opaque, tightly stop- 
pered containers. Proper safety contain- 
ers should be used for the few reagents 
that require flammable organic solvents 
of high vapor pressure. 

SPOT TEST TECHNIQUES 

Chapters 1 and 2 of Feigl's text on 
spot tests (2) give a thorough overview 
of various techniques used in conduct- 
ing spot tests. Some general guidelines 
are given in this section for the tests 
selected by the Bureau for mercury 
detection. 

As mentioned in the previous section, 
low-actinic containers should be used for 
the organic reagents to retard deteriora- 
tion. In the field, it is recommended 
that amber polyethylene dropping bottles 
with screw-cap tops be used. Even so, 
many of the organic reagents need to be 
prepared fresh for reliable results. 
Low-actinic containers are not needed for 
the 1:1 nitric acid used to dissolve the 
mercury for each test, but the container 
should be acid resistant. A Teflon^ 
fluorinated ethylene propylene (FEP) 
dropping bottle or a drop dispensing 
bottle with a screw-cap top is useful for 
this purpose. 

^Reference to specific trade names is 
made for identification only and does not 
imply endorsement by the Bureau of Mines. 



It is important that the tip of the 
eyedropper pipet used to deliver the rea- 
gents remain free from contamination. 
The tip of the pipet should not be 
touched against the receiving surface. 
The pipet tip should be no more than 1 or 
2 cm above the place where the drop is to 
be delivered to assure accurate delivery 
and avoid splashing, but the drops should 
be allowed to fall freely. Not only does 
this technique avoid contamination, but 
the size of the drops remains fairly uni- 
form, thereby allowing a semiquantitative 
comparison of mercury in the samples 
based on color intensities. 

Direct testing on surfaces in a mill or 
mine is generally not possible nor desir- 
able. A portion of the dust or material 
to be tested should be scraped from the 
surface with a spatula and placed on a 
filter paper or in a white glazed spot 
plate, a watch glass, or a micro test 
tube for attack by the 1:1 nitric acid. 
The acid is diluted with distilled water, 
generally by a factor of 3, before it is 
combined with the color-producing rea- 
gent. If the mercury is dissolved in a 
container other than filter paper, some 
of the liquid is then transferred to a 
white filter paper using an eyedropper 
pipet. If cotton is placed in the tip of 
the pipet, it will separate the liquid 
from the solids for a more interference- 
free observation of the color change. 
However, this separation is not usually 
necessary because the solution containing 
the dissolved mercury will diffuse away 
from the solids through the capillaries 
of the paper. The color-producing rea- 
gent is added to the solvent -moistened 
portion of the paper around the solids 
whether the solids are treated with the 
nitric acid directly on the paper or are 
transferred to the paper along with the 
solvent from a separate dissolution 
vessel. 

The capillary action and adsorptive 
effects of filter paper make it the 
preferred substrate for spot reactions. 
Color reactions that appear to be rel- 
atively insensitive when diluted with 
the solvent in a spot plate or test tube 
may have excellent sensitivities on an 



appropriate filter paper. This is be- 
cause the colored, soluble, or insoluble 
reaction products of the test are held 
near the site of their production by the 
capillaries of the paper and are more 
readily seen because of the white back- 
ground of the paper. Precipitation and 
filtration take place in the plane of the 
paper, resulting in a local enrichment 
and improved visibility of the colored 
reaction product. 

When the mercury is dissolved from the 
sample directly on the filter paper, as 
recommended for some procedures, an acid- 
hardened paper such as Whatman 50 or 
Schleicher and Schuell 576 is recommend- 
ed. These papers have a slow filtering 
speed, resulting in increased acid con- 
tact with the sample; they are acid- 
resistant; and they retain very fine 
precipitates on their smooth, white, 
lint -free surfaces for easy observation. 

SELECTED SPOT TESTS 

From the spot tests for mercuric ions 
listed in table 1, the Bureau selected 
the four tests described below as repre- 
sentative of those applicable to conven- 
ient field testing for sources of mercury 
vapor in the workplace. These tests were 
selected because of their simplicity, 
sensitivities, minimal interferences, and 
strong positive color changes in the 
presence of mercury. 

The sample size for each test is ap- 
proximately half of a 3- by 10-mm spatula 
spoonful. The mercuric ions for each 
test are obtained by dissolution of mer- 
cury metal or compounds from the sample 
using 1:1 nitric acid prepared by adding 
50 mL of reagent-grade concentrated ni- 
tric acid to 50 mL of distilled water. 
All chemicals should be reagent grade and 
prepared with distilled water. Once pre- 
pared, the reagents should be tested with 
a blank 1:1 nitric acid sample for mer- 
cury contamination. 

Cuprous Iodide Test 

Reagents 

1. Potassium iodide-sodium sulfite 
solution: 5 g KI and 20 g Na 2 S0 3 *7H 2 in 
100 mL water. 



2. Copper sulfate solution: 5 g CuS0 4 
•5H 2 in 100 mL IN hydrochloric acid 
(83 mL reagent-grade concentrated hydro- 
chloric acid diluted to 1 L with dis- 
tilled water). 

Reagent Paper 

The filter paper is impregnated with 
the reactive reagents in the laboratory, 
minimizing the chemicals needed in the 
field. This is done by soaking an ab- 
sorbent filter paper (e.g., Schleicher 
and Schuell 598 or Whatman 1) in the po- 
tassium iodide-sodium sulfite solution 
and then in the copper sulfate solution. 
The excess reagents are rinsed from the 
papers , and the papers are allowed to 
dry prior to their use in the field. The 
papers should last for several weeks if 
kept dry and if long exposure to direct 
sunlight or oxidizing environments is 
avoided. 

Field Procedure 

1. Add 1 or 2 drops of 1:1 nitric acid 
to the sample in a spot plate and let 
stand for 1 min. 

2. Add 3 times as many drops of dis- 
tilled water to dilute the acid. 

3. Remove a portion of the liquid with 
an eyedropper pipet, and place a drop on 
the reagent paper. A red or orange color 
indicates the presence of mercury. 

Diphenylcarbazide Test 
Reagents 

1. Diphenylcarbazide solution: 2 g 
diphenylcarbazide in 10 mL acetic acid 
and 10 mL ethanol. (Use low-actinic bot- 
tles. The solution is reddish-orange 
while effective.) 

2. Sodium pyrophosphate solution: 3 g 
Na 4 P 2 7 '10H 2 in 100 mL water. 

3. 3 pet hydrogen peroxide solution if 
chromates may be present. 

Field Procedure 

1. Add 1 or 2 drops of 1:1 nitric acid 
to the sample on a filter paper and let 
stand for 1 min. 



10 



2. Add 3 times as many drops of dis- 
tilled water to dilute the acid. 

3. Add 2 drops of sodium pyrophosphate 
solution to eliminate interferences. If 
chromates are present, a drop of 3 pet 
hydrogen peroxide may also need to be 
added. 

4. Add 1 drop of diphenylcarbazide 
solution at the edge of the solids. A 
violet or blue fleck indicates the pres- 
ence of mercury. 

Chromotropic Acid Test 



limit of 25 mg Hg 2+ per liter is ob- 
tained. Bureau tests with nitric acid 
solutions of Zn, Pb, Cu, Bi, and Cd did 
not produce a color change, This ob- 
servation is in agreement with the man- 
ufacturer's claims that there are no 
interferences for this paper. MSHA has 
selected this test paper for field 
evaluation. 

Field Procedure 

1. Add 1 or 2 drops of 1:1 nitric acid 
to the sample in a spot plate and let 
stand for 1 min. 



Reagent 

1. Chromotropic acid solution: 5 g 
sodium salt of chromotropic acid in 100 
mL distilled water. (Use low-actinic 
bottle.) 

Field Procedure 

1. Add 1 or 2 drops of 1:1 nitric acid 
to the sample on a filter paper and let 
stand for 1 min. 

2. Add 3 times as many drops of dis- 
tilled water to dilute the acid. 

3. Add 1 drop of chromotropic acid 
solution at the edge of the solids. A 
bright yellow color indicates the pres- 
ence of mercury. 

Commercial Test Paper 

Description and Characteristics 

A commercially available test paper 
sensitive only to Hg 2+ ions is manufac- 
tured by Machery, Nagel and Co., Duren, 
West Germany, and is available in the 
United States from Gallard Schlesinger 
Chemical Mfg. Corp., Carle Place, N.Y. 
The cost is under $10 for 200 strips mea- 
suring 20 by 70 mm. No information is 
given by the manufacturer about the ac- 
tive ingredient in the paper. In the 
presence of Hg 2+ ions, the grayish-brown 
paper turns white. If a capillary or 
micropipet is used to apply 10 to 20 yL 
of solution to the paper, a sensitivity 



2. Add 3 times as many drops 
tilled water to dilute the acid. 



of dis- 



3« Touch a strip of the test paper to 
the liquid or use a capillary tube to 
touch the liquid to the paper. A white 
discoloration of the paper indicates the 
presence of mercury. 

MERCURY VAPOR TEST PAPERS 

Two test papers applicable for the 
direct detection of mercury vapor — as 
opposed to mercury ions, which are 
needed for reaction with most of the 
reagents listed in table 1 — can be pre- 
pared in the laboratory. Filter paper 
impregnated with a 1 pet solution of 
palladium chloride and then dried pro- 
vides a sensitive test for traces of 
mercury vapor in air (2) . When mercury 
vapor comes in contact with the paper, 
the light brown color turns light gray to 
deep black. The stain can be made more 
visible by briefly holding the paper over 
concentrated ammonia. The formation 
of tetrammine palladium (II) chloride 
[Pd(NH 3 ) 4 Cl 2 ] changes the light brown 
paper to white, and the gray metallic 
palladium formed by the mercury vapor 
is easily seen against the white back- 
ground. The most sensitive tests are 
obtained when the paper is completely 
dry. 

A selenium sulfide test paper for mer- 
cury vapor can be prepared by bathing 
filter paper in a water solution of 
selenious acid, exposing the paper to 



11 



hydrogen sulfide, then washing and dry- 
ing it (2). Black mercuric selenide and 
mercuric sulfide are formed when the 
selenium sulfide is exposed to mercury 
vapor. 

Both mercury vapor test papers must be 
exposed to vapor for several hours if 



used as a passive monitor (J7) in order to 
detect the 0.05 mg/m 3 TLV for mercury. 
Pumping the air across the test paper 
will shorten the time required for a pos- 
itive test, and the degree of darkening 
of the selenium sulfide paper is propor- 
tional to the square root of the velocity 
of the air (7). 



PORTABLE MERCURY VAPOR DETECTORS 



Several portable, commercially avail- 
able devices for mercury vapor detec- 
tion are compared in table 2 for relia- 
ble measurement range, cost, and mode of 
mercury detection. Mercury vapor absorp- 
tion of ultraviolet light at the 253.7- 
nm wavelength is the means of measuring 
relative concentrations for the Bach- 
arach and Beckman instruments. Organic 



vapors, dust, or other components of the 
air that absorb ultraviolet light at the 
specified wavelength will give false in- 
dications of mercury, but generally this 
is not a problem. Background correction 
for broadband absorption could be added 
to the instrumentation, although this 
would add to the expense, bulk, and 
weight of the instrument. 



TABLE 2. - Portable mercury vapor detection devices 



Vendor 


Model 


Detection principle 


Reliable 
measurement 
range , ' 
mg Hg/m 3 


Approx- 
imate 
cost 

(1982) 


Bacharach Instrument Co. , 
Pittsburgh, Pa. 15238. 


MV-2 


Hg vapor absorption of UV 
light. 


0.01 - 0.2 


$1,800 


Beckman Instruments, 
Inc. , Fullerton, Calif. 
92634. 


K-23 




.005- 1 


2,200 


Bendix Corp. , Largo, Fla. 
33543. 


Tube 40 


Absorption of Hg in a tube 
causes cupric iodide color 
change to orange. 


.05 -13 


200 


Jerome Instrument Co. , 
Concord, N.H. 03301. 


401 


Absorption of Hg by Au film 
increases electrical 
resistance. 


.01- .5 


3,000 


Mine Safety Appliances, 
Pittsburgh, Pa. 15235. 


C-210 


Absorption of Hg by iodine- 
impregnated charcoal; Hg 
determined by laboratory 
analysis. 


.01- .3 


400 


National Draeger, Inc. , 
Pittsburgh, Pa. 15235. 


Mercury 


Absorption of Hg in a tube 
causes cupric iodide color 
change to orange. 


.1- 2 


400 


3M Co., St. Paul, Minn. 
55101. 


23600 


Absorption of Hg by an Au 
film which is sent to man- 
ufacturer for analysis. 


.005- .20 


( 3 ) 



1 Actual detection limits 
able measurement. 

2 Personnel mercury vapor 
3 $160 for 5 film badges. 



are generally lower than the lowest values given for reli- 
monitor (film badge). 



12 



The Jerome instrument (fig. 1) works on 
the principle that the electrical conduc- 
tivity of a gold film changes as it forms 
an amalgam with mercury vapor from the 
air (b_, 8). Interference by dust, organ- 
ic vapors, or other air components is 
avoided unless a vapor that is reactive 
with gold, e.g., chlorine, is present. 
The 3M Co.'s personnel film badge moni- 
tors also work on the principle of mer- 
cury collection by gold, but the mercury 
is measured in the lab using electrical 
resistivity ( 5_) . 

The remaining three mercury vapor de- 
tection systems listed in table 2 — sold 
by Bendix Corp., Mine Safety Appliances, 
and National Draeger, Inc. — use the 
chemical reaction of mercury with iodine 



to detect the vapor. In the Bendix 
and National Draeger absorption tubes, 
the red to orange color of the cupro- 
tetraiodomercuriate is the indicator of 
the presence of mercury vapor. The Mine 
Safety Appliances system uses iodine im- 
pregnated charcoal to trap the mercury, 
which must then be chemically eluted from 
the charcoal and determined in the labo- 
ratory. Although the lower limit of the 
reliable measurement range of the Nation- 
al Draeger tube is 0.1 mg/m 3 , the actual 
detection limit — the level at which the 
characteristic red coloring begins to ap- 
pear — is below the 0.05 mg/m 3 TLV set by 
ACGIH. A comparative study of personal 
mercury sampling devices has been report- 
ed by McCammon (4). 




FIGURE 1. - Gold-film analyzer for locating sources of mercury vapor. 



13 



For the purpose of on-site location of 
mercury vapor sources , the need to return 
to the laboratory for mercury determina- 
tion would eliminate from consideration 
the 3M Co. and Mine Safety Appliances 
detectors. The absorption tubes sold by 
Bendix and by National Draeger show a 
cumulative mercury level, with the red 
color advancing through the tube with 
continued exposure to mercury vapor, and 
therefore lack the ability to show 



fluctuations in mercury vapor concen- 
trations from one minute to the next 
as the device is moved from place to 
place. The most useful devices for the 
intended purpose are the more expensive 
battery-powered ultraviolet and gold- 
film-resistivity instruments. Each in- 
strument has a survey mode that contin- 
uously samples the air, denoting areas of 
high mercury concentration near sources 
of mercury vapor contamination. 



PORTABLE ANALYTICAL INSTRUMENTS 



The portable analytical instruments 
listed in table 3 have the capability, 
except for the Perkin-Elmer (formerly 
Coleman) model MAS-50A, of determining 
other elements in addition to mercury. 
The MAS-50A is designed specifically for 
the cold-vapor atomic-absorption deter- 
mination of mercury ( 1_) . 

Samples must be taken from the area 
being surveyed before instrumental 
analysis can be performed using the MAS- 
50A. This is true also for the Graphic 
Controls ion-selective electrode and 
the Hach Chemical ultraviolet spectro- 
photometer. In each case the mercury 
must be dissolved from the sample and 
chemically treated. When the cold-vapor 



atomic-absorption method is used, the 
mercuric ion is reduced to the metallic 
state and then vaporized so that mercury 
can be determined by atomic absorption 
at the 253.7-nm wavelength. The ion- 
selective electrode method uses a sens- 
ing component for the direct determina- 
tion of mercuric ion activity, or the 
mercuric ion may be determined indirectly 
by titration with iodide until an excess 
of iodide is detected by an iodide- 
selective electrode (10). However, ac- 
curate determination of mercury using 
the ion-selective electrode may be diffi- 
cult because of interferences from 
chloride, bromide, iodide, cyanide, 
thiocyanates, sulfide, and silver. The 
ultraviolet spectrophotometric method is 



TABLE 3. - Portable analytical instruments 



Vendor 


Model 


Type of instrument 


Approximate 
cost (1982) 


Columbia Scientific, 
Austin, Tex. 78766. 


700 




$8,000 


Graphic Controls 
Corp. , Buffalo, 
N.Y. 14240. 


PHI 96100 


Ion-selective electrode. . 


300 


Hach Chemical Co. , 
Loveland, Colo. 
80537. 


DR/2 




750 


Panametrics, Inc., 
Waltham, Mass. 
02154. 


Panalyzer 
4000 




6,400 


Perkin-Elmer Corp. , 
Oakbrook, 111. 
60521. 


MAS-50A 


Cold-vapor atomic absorp- 
tion analyzer. 


2,400 



14 



indirect: Dithizone is used as the ac- 
tive ingredient to complex the mercuric 
ions, and the complex is then extracted 
into chloroform (3). The mercury concen- 
tration is determined at the point where 
an excess of dithizone gives an absorb- 
ance at the 610-nm wavelength. (For an 
indication of the many interferences that 
are possible when dithizone is used, see 
table 1). The usefulness of any of 
these three techniques (cold-vapor atom- 
ic absorption, ion-selective electrode, 
and ultraviolet spectrophotometric) for 
on-site location of mercury vapor sources 
is greatly restricted by the need to col- 
lect samples and chemically treat the 
samples to obtain results. 

The utility of fluorescent X-ray spec- 
trography for determining trace concen- 
trations of heavy metals in various 
matrixes is well documented. The devel- 
opment of portable X-ray instrumentation 
has extended this application to in situ 
determinations of trace elements in ore 
samples (9). Mercury concentrations of 
0.7 pet Hg in a 1-g sample can be deter- 
mined. Sensitivity is a function of the 
detector resolution and the activity 
of the radioisotope used for sample 
excitation. 

The type of detector used in a portable 
X-ray analyzer greatly affects both cost 
and sensitivity. Scintillation detectors 
and proportional counters have long been 
used to detect X-rays in analytical in- 
struments. The two devices listed in ta- 
ble 3 use sealed proportional counters. 
They are rugged, inexpensive, and provide 
moderate sensitivity in portable devices 



when coupled with balanced filters to 
discriminate the X-rays of interest from 
a complex spectral background. Only one 
element is determined for each set of 
balanced filters. 

The alternative approach is to use a 
device similar to the "X-site" alloy- 
sorting instrumentation marketed by Kevex 
Inc. This system uses a solid-state 
semiconductor detector (lithium-drifted 
silicon) , and simultaneous multielement 
determinations are therefore possible. 
The probe head containing the detector is 
portable, but the required power supply 
and the computer hardware are not. The 
silicon detector gives the system greater 
flexibility for resolving complex spectra 
than a proportional counter has, but the 
detector requires constant liquid nitro- 
gen cooling and costs much more than a 
proportional counter. 

The only commercially available porta- 
ble X-ray analyzer with a solid-state de- 
tector is a gold analyzer marketed by 
Ortec Inc. It has a germanium detector, 
requires liquid nitrogen cooling, and 
costs about $60,000. Its sensitivity for 
gold is less than 0.1 pet Au in ore sam- 
ples, and its sensitivity for mercury is 
probably comparable, because gold and 
mercury X-rays have similar energies. 
The germanium detector is able to detect 
higher energy X-rays than the proportion- 
al counter, and fewer interferences exist 
for the K-alpha X-rays of mercury; there- 
fore, consistently lower detection limits 
for mercury in different types of samples 
would be expected. 



CONCLUSIONS 



Of the more than 50 reagents for mer- 
cury identification spot tests that were 
examined, many could be applied for the 
identification of sources of mercury 
vapor in mines and mineral processing 
plants. Poor shelf life, nonselectivity , 
and lack of sensitivity would eliminate 
some from consideration. At least two 
spot tests that react to mercury vapor 
are available; the others require the 
presence of mercury ions for positive 
test results. One commercially available 



mercury test paper, sensitive only to 
mercuric ions, appears to best meet the 
need for locating sources of mercury 
vapor in the workplace. 

Portable mercury vapor detectors that 
could be used for real-time surveying in 
a mine or mill range in cost from $1,800 
to $3,000. Less expensive vapor detec- 
tion devices require laboratory backup or 
cannot provide the flexibility needed to 
pinpoint a mercury vapor source. 



15 



Portable analytical instrumentation is 
also limited for field use by the need 
for sample collection, dissolution, and 
chemical treatment in every case except 
for the X-ray analyzers. However, the 
portable X-ray analyzers are the most ex- 
pensive of all the detection systems ex- 
amined, ranging from $6,000 to $8,000 or 
more. 



Methods of identifying sources of mer- 
cury vapor in mines and mineral process- 
ing plants are readily available with no 
need for further research and develop- 
ment. The inexpensive, commercially 
available mercury test paper mentioned 
above appears to have no interferences 
and requires minimal skills to obtain re- 
liable results. 



REFERENCES 



1. Dumarey, R. , R. Heindryckx, R. 
Dams, and J. Hoste. Determination of 
Volatile Mercury Compounds in Air With 
the Coleman MAS-50 Mercury Analyzer Sys- 
tem. Anal. Chim. Acta, v. 107, 1979, 
pp. 159-167. 

2. Feigl, F. Spot Tests. Elsevier 
Pub. Co., New York, v. 1, 1954, 518 pp. 

3. Kolthoff, I. M. , and P. J. Elving, 
eds. Treatise on Analytical Chemistry. 
John Wiley & Sons, Inc., New York, part 
II, v. 3, 1961, 380 pp. 

4. McCammon, C. S., Jr., S. L. Ed- 
wards, R. D. Hull, and W. J. Woodfin. A 
Comparison of Four Personal Sampling 
Methods for the Determination of Mercury 
Vapor. J. Am. Ind. Hyg. Assoc, v. 41, 
1980, pp. 528-531. 

5. McCammon, C. S., Jr., and J. W. 
Woodfin. An Evaluation of a Passive Mon- 
itor for Mercury Vapor. J. Am. Ind. Hyg. 
Assoc, v. 38, 1977, pp. 378-386. 

6. McNerney, J. J., and P. R. Buseck. 
Geochemical Exploration Using Mercury Va- 
por. Econ. Geol. Bull. Soc Econ. Geol. , 
v. 68, 1973, pp. 1313-1320. 

7. Nordlander, B. W. Selenium Sul- 
fide — A New Detector for Mercury Vapor. 
Ind. Eng. Chem. , v. 19, 1927, pp. 518- 
521. 



8. Ohkawa, T., H. Uemoyama, and M. 
Kondo. (Mercury Analysis in Ambient Air 
by Means of Thin Gold Resistors.) Eisei 
Kagaku, v. 22, 1976, pp. 11-19. 

9. Rhodes, J. R. , C. S. Barrett, 
D. E. Leyden, J. B. Newkirk, P. K. 
Predecki, and C. D. Ruud, eds. Advances 
in X-Ray Analysis. Plenum Press, New 
York, v. 23, 1980, 390 pp. 

10. Sekerka, I., and J. F. Lechner. 
Behavior of Ion Selective Electrodes 
Based on Silver or Mercuric Sulfide Sel- 
enide and Telluride. Anal. Lett., v. 9, 
1976, pp. 1099-1110. 

11. Welcher, F. J. Organic Analytical 
Reagents. D. Van Nostrand Co., Inc., New 
York, v. 1, 1947, 442 pp. 

12. . Organic Analytical Rea- 
gents. D. Van Nostrand Co., Inc., New 
York, v. 2, 1947, 530 pp. 

13. . Organic Analytical Rea- 
gents. D. Van Nostrand Co., Inc., New 
York, v. 3, 1947, 581 pp. 

14. . Organic Analytical Rea- 
gents. D. Van Nostrand Co., Inc., New 



York, v. 4, 1948, 624 pp. 



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